The desire to put a more powerful gun on a tank has always been: along with protection and mobility, firepower is one of the main characteristics of a tank. From the history of the development of tanks, it is known that with each new generation, the caliber of the gun increased more and more. Today, Western tanks have a cannon caliber of mainly 120 mm, and Soviet (Russian) ones - 125 mm. So far, no one has dared to install a gun of a higher caliber. In the West, tank guns of 140 mm caliber are being worked out, and in the Soviet Union (Russia) several variants of a tank gun of 152 mm caliber were created, but none of the projects was implemented. What is the reason for the rejection of such a high caliber cannon on tanks?
Tank dangerous targets and weapons used to destroy them
The tank is a versatile well-protected and mobile weapon of the battlefield, capable of conducting both close and long-range fire combat with the direct support of mobile combined arms units, and independent operations to implement and develop deep breakthroughs and destroy enemy military infrastructure.
The main targets for the tank are tanks, artillery (self-propelled guns), anti-tank systems, lightly armored vehicles, fortified defense units, RPG crews and enemy manpower, that is, targets that are in line of sight from the tank. All these targets are more or less dangerous for the tank; against each of them the tank must have its own antidote. So, in the Arab-Israeli war of 1973, tank losses were distributed as follows: from ATGM fire - 50%, aviation, RPGs, anti-tank mines - 28%, tanks - 22%. Losses of armored vehicles (tanks, infantry fighting vehicles, armored personnel carriers) during active battles in Donbass in 2014-2016 amounted to 2596 units, of which from MLRS and artillery fire - 45%, ATGM and RPG - 28%, tanks - 14% and mine explosions - 13%.
To defeat the entire set of targets, the tank has main, auxiliary and additional weapons.
To suppress the calculations of RPGs, lightly armored targets and enemy manpower, auxiliary and additional armament of the tank is intended, to suppress lightly armored targets at long distances (up to 5000 m), guided missiles fired from a cannon are used. Auxiliary and additional weapons on the tank can be improved by installing automatic small-caliber cannons and automatic grenade launchers.
For a tank gun, the main targets are tanks, artillery (self-propelled guns), anti-tank systems and well-fortified enemy defense points. To suppress targets, the gun ammunition includes four types of ammunition: armor-piercing sabot, cumulative, high-explosive fragmentation projectiles and guided missiles. In this case, the firepower of the BPS and OFS is determined by the kinetic energy of the projectile, and the KMS and UR are determined by the destructive effect of the cumulative jet.
The effectiveness of tank ammunition
For the BPS, the initial velocity of the projectile is decisive, and for the OFS, the velocity and mass (caliber) of the projectile, since the caliber affects the mass of the explosive and submunitions delivered to the target. In this case, the kinetic energy of the BPS and OFS depends on the square of the projectile speed and is directly proportional to its mass, that is, an increase in the projectile speed, and not its mass, gives a greater effect.
For the KMS and UR, the caliber of the gun is not of fundamental importance, since it only gives the opportunity to increase the mass of the explosive, and for the UR also the stock of rocket fuel. Therefore, it is more promising to increase not the caliber, but the initial velocity of the projectile, determined by the muzzle energy of the gun, which can be higher not only by increasing the caliber.
Considering the effectiveness of BPS, KMS and UR in terms of hitting armored targets, it should be noted that, due to the low speed of the KMS and UR, a good antidote has been found against them - dynamic and active protection. How the confrontation between them will end is still unknown.
The use of hypersonic BPSs for engaging armored targets, which are less susceptible to the effects of dynamic and active protection in comparison with cumulative ammunition, may be more effective, and for them the defining role is not the caliber, but the initial velocity of the projectile.
In addition, an increase in the initial velocity of a projectile with a propelling powder charge has a physical limitation to 2200-2400 m / s, and a further increase in the mass of the charge due to an increase in the caliber does not give an increase in efficiency, in this regard, the use of new physical principles of projectile throwing is required.
Such areas can be the development of electrothermochemical (ETS) guns using light gases (hydrogen, helium) as a propellant charge, providing an initial projectile velocity of 2500-3000 m / s or electromagnetic guns with an initial projectile velocity of 4000-5000 m / s. Work in this direction has been going on since the 70s, but the acceptable characteristics of such "gun-projectile" systems have not yet been achieved due to problems in creating electric energy storage units with high volumetric density in the required dimensions.
The development of the effectiveness of the OFS can also go not only by increasing the caliber, but by creating more advanced explosives and the development of a new generation of the OFS with the provision of trajectory detonation of the projectile in the zone of reliable destruction using a proximity fuse or with a remote fuse at a given range, introduced into the projectile at the moment loading the gun, work on which has been going on since the 70s.
Increasing the caliber of the cannon naturally gives an increase in firepower, but at a too high cost. This comes at the cost of complicating the design of the tank and the automatic loader due to the placement of a larger gun and powerful ammunition, an increase in the booked volume, an increase in the mass of armor, guns, ammunition and automatic loader assemblies, as well as a possible reduction in the amount of ammunition.
Installation of a 152-mm cannon on the Boxer and Object 195 tanks
An increase in firepower due to an increase in the caliber of the gun leads to a significant increase in the mass of the tank and, as a result, to a decrease in its protection and mobility, that is, in general, the effectiveness of the combat vehicle decreases.
An example is the installation on the promising tank "Boxer" being developed at the KMDB in the mid-80s, the "semi-extended" 152-mm cannon 2A73. The development of the tank began with the installation of a 130-mm cannon, but at the request of the GRAU, the caliber was increased and a 152-mm 2A73 cannon with separate loading was developed for the tank. For the safety of the crew, the ammunition load from the turret was moved to a separate armored compartment between the fighting compartment and the MTO, which led to the lengthening of the tank hull, the development of complex overall units of the automatic loader and an increase in its mass. The mass of the tank began to fall out for 50 tons, to reduce it, titanium began to be used in the frontal booking package and in the manufacture of the chassis of the tank, which complicated the design and increased the cost.
Subsequently, they switched to unitary ammunition and placed it in the fighting compartment. The mass of the tank decreased, but the placement of ammunition together with the crew reduced the survivability of the tank. With the collapse of the Union, work on the tank was curtailed.
An attempt to install the same "semi-extended" 152-mm cannon 2A83 was made on the Object 195 tank, which was being developed at Uralvagonzavod in the early 90s, with the crew in an armored capsule in the tank hull. This project was also not implemented and closed. I suppose that due to problems with the mass of the tank due to the use of a 152 mm cannon and the impossibility of realizing the required characteristics in a given mass of the tank. On the Armata tank, apparently, taking into account the experience gained in these projects, they also abandoned the installation of a 152-mm cannon.
Attempts to install a 152-mm cannon on a tank either in the Soviet (Russian) or in the Western schools of tank building did not lead to positive results, including due to the impossibility of achieving an optimal combination of characteristics in terms of firepower, protection and mobility of the tank.
Increasing firepower by increasing the caliber of the gun is hardly promising; this will have to be achieved by creating more effective cannon-projectile systems using new ideas and technologies that allow increasing firepower without reducing the tank's protection and mobility.
